Hazelnuts are an economically important nut which is consumed world-wide.It is prone to infection by Aspergillus flavus and contamination with aflatoxins.Taking Tukey’s hazelnuts as a research object,the objective of...Hazelnuts are an economically important nut which is consumed world-wide.It is prone to infection by Aspergillus flavus and contamination with aflatoxins.Taking Tukey’s hazelnuts as a research object,the objective of this study were to(a)quantify respiration rates and(b)dry matter losses(DMLs)and(c)aflatoxin B_(1)(AFB_(1))contamination of naturally stored shelled hazelnuts at different temperatures and water availabilities.Subsequently,shelled hazelnuts were inoculated with additional A.flavus inoculum prior to storage to examine effects on dry matter losses and on AFB_(1) contamination.Maximum respiration of hazelnuts and associated mycoflora was under wetter conditions of 0.90~0.95 water activity(aw=12.5%~18%moisture content).This resulted in between approx.10%DML at 25 and 30℃after 5 days storage.Inoculation and storage of shelled hazelnuts+A.flavus inoculum resulted in similar patterns of respiration with optimal levels at 25~30℃and>0.90 aw.Indeed,AFB_(1) contamination was highest at the maximum water levels tested of 0.90 aw.Indeed the contamination level exceeded the legislative limits set by the EU for AFB_(1) contamination of these nuts.Correlation between DMLs and all the AFB_(1) data in both sets of studies showed that very small changes in DML due to poor drying or storage of≥0.6%resulted in AFB_(1) contamination levels exceeding the EU legislative limits.Thus,efficient drying and safe monitored storage is necessary to minimise the risk of AFB_(1) contamination in this economically important commodity and to avoid exposure of consumers to such toxins.展开更多
The objective of this study was to examine the effect of gaseous ozone(O_(3))on(a)germination,(b)mycelial growth,(c)aflatoxin B1(AFB1)production by strains of Aspergillus flavus at different water activity(aw,0.89~0.9...The objective of this study was to examine the effect of gaseous ozone(O_(3))on(a)germination,(b)mycelial growth,(c)aflatoxin B1(AFB1)production by strains of Aspergillus flavus at different water activity(aw,0.89~0.97=13.1%~24%moisture content)and 25 oC in vitro.In addition,taking Egyptian peanuts as a research object,shelled peanuts at 0.93 aw were inoculated with two concentrations of A.flavus conidia(103,105 conidia/g)and exposed to gaseous O_(3) and then stored.In all cases,exposure was for 30 min at 6 L/min.Generally,>100 ppm O_(3) significantly inhibited conidial germination of A.flavus strains(EGP-B07;SRRC-G 1907)on a defined yeast sucrose medium within 48 hrs.However,exposure of growing colonies of A.flavus to O_(3) with up to 300 ppm,had no effect on subsequent colony extension.The same concentration significantly affected AFB1 production,but only at 0.89 aw.Populations of both A.flavus strains in stored shelled peanuts exposed at 0.93 aw were significantly decreased at 100~400 ppm O_(3).However,AFB1 production was only significantly reduced in the 400 ppm O_(3) treatments at both inoculum load levels.These results are discussed in the context of O_(3) gas use for controlling A.flavus populations and AFB1 in shelled peanuts post-harvest.展开更多
文摘Hazelnuts are an economically important nut which is consumed world-wide.It is prone to infection by Aspergillus flavus and contamination with aflatoxins.Taking Tukey’s hazelnuts as a research object,the objective of this study were to(a)quantify respiration rates and(b)dry matter losses(DMLs)and(c)aflatoxin B_(1)(AFB_(1))contamination of naturally stored shelled hazelnuts at different temperatures and water availabilities.Subsequently,shelled hazelnuts were inoculated with additional A.flavus inoculum prior to storage to examine effects on dry matter losses and on AFB_(1) contamination.Maximum respiration of hazelnuts and associated mycoflora was under wetter conditions of 0.90~0.95 water activity(aw=12.5%~18%moisture content).This resulted in between approx.10%DML at 25 and 30℃after 5 days storage.Inoculation and storage of shelled hazelnuts+A.flavus inoculum resulted in similar patterns of respiration with optimal levels at 25~30℃and>0.90 aw.Indeed,AFB_(1) contamination was highest at the maximum water levels tested of 0.90 aw.Indeed the contamination level exceeded the legislative limits set by the EU for AFB_(1) contamination of these nuts.Correlation between DMLs and all the AFB_(1) data in both sets of studies showed that very small changes in DML due to poor drying or storage of≥0.6%resulted in AFB_(1) contamination levels exceeding the EU legislative limits.Thus,efficient drying and safe monitored storage is necessary to minimise the risk of AFB_(1) contamination in this economically important commodity and to avoid exposure of consumers to such toxins.
文摘The objective of this study was to examine the effect of gaseous ozone(O_(3))on(a)germination,(b)mycelial growth,(c)aflatoxin B1(AFB1)production by strains of Aspergillus flavus at different water activity(aw,0.89~0.97=13.1%~24%moisture content)and 25 oC in vitro.In addition,taking Egyptian peanuts as a research object,shelled peanuts at 0.93 aw were inoculated with two concentrations of A.flavus conidia(103,105 conidia/g)and exposed to gaseous O_(3) and then stored.In all cases,exposure was for 30 min at 6 L/min.Generally,>100 ppm O_(3) significantly inhibited conidial germination of A.flavus strains(EGP-B07;SRRC-G 1907)on a defined yeast sucrose medium within 48 hrs.However,exposure of growing colonies of A.flavus to O_(3) with up to 300 ppm,had no effect on subsequent colony extension.The same concentration significantly affected AFB1 production,but only at 0.89 aw.Populations of both A.flavus strains in stored shelled peanuts exposed at 0.93 aw were significantly decreased at 100~400 ppm O_(3).However,AFB1 production was only significantly reduced in the 400 ppm O_(3) treatments at both inoculum load levels.These results are discussed in the context of O_(3) gas use for controlling A.flavus populations and AFB1 in shelled peanuts post-harvest.
